1. Field of the Invention
The invention relates to a rock drill for hand-guarded rotary hammers, percussion drilling machines, rotary machines and the like.
The invention relates to a rock drill according to the preamble of claim 1.
2. Related Art
Conventional rock drills consist of a drill shank and a drill head in which a carbide cutting element, roof-shaped in side view and extending over the entire drill nominal diameter, is inserted (see, for example, DE 29 12 394 A1). In addition to this “main cutting tip”, secondary cutting tips, likewise arranged in a roof shape, may also be arranged, and these secondary cutting tips may be arranged, for example, in a cross shape, that is to say while including a right angle, or also in an x-shape (for example EP 0 657 617 A1). The drill head has axially running slot-shaped recesses in which such cutting tips are inserted and brazed in place.
In order to achieve adequate endurance of the carbide tips, they must have a certain minimum thickness, a factor which necessitates a correspondingly wide locating slot for the carbide tips. However, such a locating slot extending over the entire diameter, and possibly transversely thereto, for such a carbide cutting tip having main and secondary lips reduces the available wall thickness for supporting the respective main and/or secondary lips, which is of importance in particular in drilling tools having a smaller nominal diameter, for example less than 10 mm. This applies in particular when the drill head is of very slim design for forming large flute cross sections for drillings to be removed (see, for example, DE 197 34 094, FIGS. 4 and 7).
In multi-start conveying helices, the drillings transport from the drill head into the conveying helix flutes is effected by appropriate recesses in the drill head. The recesses also weaken the drill head with regard to the support of the carbide cutting tips used.
DE 197 53 731 A1 has disclosed a rock drilling tool in which, in order to improve the conveying properties, main and secondary conveying helices are formed, so that, in a two-start conveying helix for example, a type of four start conveying helix is produced by the secondary conveying web present in each case. A transversely inserted, roof-shaped carbide cutting tip results in each case in two main conveying flutes which are subdivided into a plurality of secondary conveying flutes by the secondary webs. With one secondary conveying helix in one main conveying flute, two secondary conveying flutes are therefore formed, that is to say a total of four secondary conveying flutes in the case of a two-start conveying helix (see, for example, FIGS. 1 and 2 of DE 197 53 731 A1).
The access to each secondary conveying flute is achieved by an extremely thin drill head, which is achieved by a straight, axially parallel runout of the conveying helix in the region of the drill head.
Drilling tools and in particular rock drills which have a drill head made entirely of carbide have been disclosed, the drill head being provided with intimated drillings flutes which lead to the individual drillings flutes in the conveying helix (DE 43 39 245 A1). Used in a further tool in this respect according to DE 197 09 771 A1 is, for example, a cross-shaped carbide drilling head which has main and secondary lips, the diameter over the secondary lips being slightly smaller than the nominal diameter of the drill. In this rock drill, the one-piece drill head of carbide can be attached with an essentially flat connecting surface to a drill core (not shown in any more detail) by means of a brazed or welded joint. In this way, four drillings disposal flutes are formed.
Finally, DE 197 07 115 A1 shows a rock drill in which a star-shaped carbide insert formed in one piece is embedded in corresponding axially [sic] longitudinal grooves in the drill head. The use of only three lips in the exemplary embodiment of this publication permits three disposal flutes, but with corresponding weakening of the drill head at the supporting embedding of the carbide insert.